Rubbers are frequently employed in fluid containment applications where a flexible yet relatively impermeable barrier is needed for fluid containment. For example, rubber may be used to keep air in a vehicle tyre, petrol in a vehicle fuel supply hose, or as a pipeline liner to prevent corrosive chemicals from attacking a steel pipeline.
In such applications, the flexibility of the rubber is a highly desirable feature, as is the impermeability of the rubber to the fluid that the rubber article is being used to contain.
EP 1 500 678 discloses a rubber composition for inner liners for tyres comprising a rubber selected from diene-based synthetic rubbers and natural rubber having a glass transition temperature of −55° C. or lower and an organized lamellar clay material. The rubber composition exhibits durability at low temperatures combined with resistance to permeation of air.
U.S. Pat. No. 4,911,218 and U.S. Pat. No. 5,049,609 each disclose a composition comprised of a polyvinylalcohol coating and at least one water-insoluble particulate organic or inorganic material having a plate like structure. Preferred particulate materials are flake mica and flake glass. Also disclosed is a rubber tyre having one of its surfaces coated with the composition.
U.S. Pat. No. 6,034,164 discloses a polymer nanocomposite composition having sufficiently low permeability to be used as a tyre inner liner prepared by blending a layered material with a metal processible non-ionic first polymer having a number average molecular weight greater than 50,000 g/mole and a second non-ionic polymer compatible with the first polymer and having a number average molecular weight less than that of the first polymer. Layered materials are disclosed as swellable layered structures such as clay minerals.
JP 2000-080207 discloses a process for forming a clay-rubber composite in which the clay mineral is uniformly dispersed in the rubber.
JP 61-120868 discloses a paint for repairing reinforced concrete with impermeability to gas by mixing 5 to 20% glass flake with a silicone rubber.
In the prior art, the provision of improved permeability for a rubber article used for containment requires either the application of a separate coating layer to the rubber article, or a process involving the swelling of a layered clay prior to its incorporation into the rubber article
Hence it can be seen that there is a is a requirement for simplified methods for producing rubber articles used for fluid containment applications where the impermeability of the rubber article to the contained fluid is improved. There is also a need to provide such rubber articles without significant loss in the flexibility of the rubber article.